Premade heel unit for shoes and a method of making the same



July 28, 1970 BENT-OVE OLSEN 3,522,345

PREMADE HEEL UNIT FOR SHOES AND A METHOD OF MAKING THE SAME Filed Oct.23. 1967 Fig.1

United States Patent 01 fice 3,522,345 Patented July 28, 1970 US. Cl.264-273 2 Claims ABSTRACT OF THE DISCLOSURE A method of making heelunits for shoes is disclosed. The heel unit is prefabricated from arubber heel and a heel base of a synthetic plastic material, the heelbase being formed by injection molding of a synthetic thermoplasticresin. The rubber heel is provided with undercut openings whichcommunicate with the heel base and, when filled with plastic, providemeans to secure the parts together. An outsole may also be attached tothe heel base by providing it with undercut openings in the heel area,which openings communicate with the mold cavity. When the heel base isformed by the injection molding process, the plastic is inserted throughthe outsole and fills the undercut openings to hold the parts securelytogether.

BACKGROUND OF THE INVENTION This invention relates to means for joiningparts, specially parts of difierent materials, one of said materialspreferably being a thermoplastic resin. More specifically, the presentinvention relates to the making of a composite heel unit for shoes and acomposite heel unit with a sole for shoes.

In the prior art of making heels for shoes the heel area is trimmed anda leather heel base nailed to the heel seat. Then a rubber heel isplaced on the base and nailed or cemented thereon whereafter the heeland sole are smoothed. Often, the base and heel are nailed in one stepto the heel seat.

SUMMARY OF THE INVENTION In order to facilitate the manufacture of shoesthe present invention has for an object to prefabricate a heel unitcomprising a rubber heel and a heel base of a synthetic plastic materialattached to said rubber heel. The heel unit is formed by injectionmoulding the base in a mould containing the premade rubber heel part,the heel part being provided with undercut openings which, when filledwith the synthetic plastic, provide means to securely hold the partstogether upon setting of the synthetic plastic material.

According to the invention, it is further possible to premake a unitcomprising a heel and an outsole by providing said outsole in the heelarea with tapered undercut openings. The wider parts of said openingsare faced away from the heel and the outsole is arranged over the mouldwith the rubber heel. A synthetic plastic is then injected into themould cavity for said heel base through said openings in the outsole.Upon setting of the synthetic plastic the three parts are securely heldtogether.

It is to be understood that the heel base may be formed by any suitablemethods known in the art of manufacture of synthetic plastic articles.Also, many different synthetic plastic products may be used butthermoplastic resins are preferred for the above mentioned purpose.

It should further be pointed out that the above outlined method forpremaking shoe parts may as well be used for joining other parts, forinstance for joining a thermoplastic resin to a metal.

BRIEF DESCRIPTION OF THE DRAWING The invention will be more closelydescribed in the following in connection with the attached drawing inwhich:

FIG. 1 is a perspective view of a heel unit according to the invention;

FIG. 2 is a cross section through a premade unit comprising a heel unitand an outsole attached thereto;

FIG. 3 schematically and in cross section shows a mould after forming ofa heel unit therein.

DESCRIPTION OF PREFERRED EMBODIMENTS Now, referring to FIG. 1, 1designates a heel unit comprising a rubber heel 2 and a heel base 3 of asynthetic plastic material, such as a thermoplastic resin, bonded to therubber heel. The heel and the base are bonded by resin having penetratedpremade openings 4 in the rubber heel during the moulding of the base.During the moulding process, ejector pins 5 FIG. 3 are preferablyinserted a short distance, e.g. 0.004 inch to 0.008 inch, into theopenings in the rubber heel in order to prevent any resin from reachingthe outside of the outside of the rubber heel during moulding. Sevensuch openings in the rubber heel are sufficient to securely hold theheel parts together when arranged as shown in the drawing.

As shown in FIGS. 2 and 3, the openings in the rubber heel are undercutand tapered, with the wider part of said openings facing outwardly inorder to lock the set resin to the rubber heel. Said openings are formedin the rubber heel in making the same. It should also be understood thatthe rubber heel is vulcanized prior to moulding the base thereto.

FIG. 2 further shows how an outsole 7 can be joined to the heel unit byinjecting the resin through undercut openings 8 in the heel seat 9 ofthe sole 7. In this manner the shoe manufacturer has a complete premadeunderpart for a shoe whereby several steps in the shoe making areeliminated. To make this modified heel unit, the rubber heel 2 isinserted in the mould against the pins 5 with the pins again blockingthe undercut openings 4. The outsole 7 is then positioned over the mouldand pressed against the same by means of a supporting member (not shown)and resin is injected into the mould cavity formed between the heel 2and the outsole 7, the resin being inserted through the openings 8 inthe outsole. After setting of the resin, the movable part 6 of the mouldFIG. 3 is withdrawn, the heel unit formed in the mould being ejected bymeans of the ejecting pins 5, which are movable with respect to mold 6.

While the invention has been described with reference to the structureherein disclosed it is not to be confined to such details, but isintended to cover such modifications or changes as may come within thescope of the following claims.

What I claim is:

1. A method of making a composite heel unit consisting of a heel partand a heel base, the method including (a) providing a heel part having afirst surface adapted to face away from a heel base and a second surfaceadapted to face said heel base;

(b) forming openings through said heel part, said openings beingundercut and tapered to provide wide ends for said openings at saidfirst surface;

(c) inserting said heel part in a mould cavity with said first surfacebeing placed against a bottom wall of said cavity;

(d) closing the wide ends of said openings in said References Citedfirst surface by inserting a short distance therein cor- UNITED STATESPATENTS responding ejector pins, said pins sealing said openings byannularly contacting at least a portion of gg g 264-476 the taperedundercut surface of sald openlngs; 5 2,298,365 10/1942 Gits closlng Saldmould W; 2 3 274 1/1945 Luth 2 4 274 X (f) injecting a setting syntheticplastic material into 2923 976 2/1960 Strauss the Volume Of Said mouldcavity left unfilled by said 3 17 :49 4 19 5 Fen-aim 264 32 X heel part,said plastic material contacting said sec- 3 2 45 8/1966 Sta fii 7 X 0ndsurface, filling said volume and penetrating said 10 openings to fillsaid openings and the Wide ends FOREIGN PATENTS thereof; and 751,3146/1956 Great Britain.

(g) ejecting the composite heel unit thus formed after the setting ofsaid plastic material by means of said 5 ROBERT WHITE, PrimaryEXamillfir ejector pins. A. M. SOKAL, Assistant Examiner 2. The methodof claim 1, wherein the injection of v said plastic material comprisesthe step of injecting a thermosetting resin. 18-2, 36; 264-261, 274,276, 334

